Process of making contact sulfuric acid



H. F. MERRIAM.

PROCESS OF MAKING CONTACT SULFUR IC ACID.

APPLICATION FILED OCT 26- I920;

Patented July 12, 1921.

, MuJooU kuhmu zou kuinjm UNITED STATES PATENT OFFICE.

HENRY F. MERRIAM, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR T0 GENERAL CHEMI- CAL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PROCESS OF MAKING CONTACT SULFURIC ACID.

Specification of Letters Patent.

Patented July 12, 1921.

Application filed October 26, 1920. Serial No. 419,599.

To all whom it may concern Be it known that I, HENRY F. MERRIAM, a citizen of the United States, and resident of Maplewood, Essex county, New Jersey, have invented certain new and useful Improvements in Processes of Making'Contact Sulfuric Acid, of which the following 1s a specification.

The new process is carried out in appara-' tus which is diagrammatically set forth in the drawing. In this drawing 3 represents the sulfur burner. This burner may consist of a'Vesuvius burner suitably modified for the burning of sulfur under the conditions hereinafter to be described. In this burner 3 a gas is formed which will, roughly speaking, be approximately an 8% S0 gas having a temperature .of above 1Q00 F. For the purpose of this specification the temperature of the gas leaving the burner will be indicated as 1000 F. The air required to support combustion in the burner 3 and to form part of the gas therein is refer-ably dry and to that end the air is first passed through a drying tower l and is then conveyed by a Connersville or other positive pressure type of .blower or fan 2 into the burner 3. The hot gases from the burner 3 are passed through air cooled pipes constituting the cooler 4 by virtue of which the temperature of the gases is somewhat reduced but is nevertheless conserved at ap- I proximately 7 50 F. under conditions where hazardous condensation of sulfuric. acid, when present, is minimized. From cooler 4 the gases still retaining their original heat to the extent of 7 50 F. enter the converter or contact chamber 5, wherein the mixed S0 and air passing over or through platinum contact material is partially converted into S0 Considerable heat is generated in this converter 5 and the gases leaving it have a temperature of approximately 1050 F. The gases, now consisting of S0 S0 and air, pass through a cooler 6 of the same general ty e and constructlon as cooler 4 but of Sn cient capacity to bring the temperature of the gases down to about 750 F., at which temperature they enter a second converter 7. In the second converter 7 the conversion ofSO to S0, is practically cornpleted so that as the ases emerge therefrom i being continuously withdrawn from said absorber 9% produced.

It will be observed from the foregoing description that during the entire progress of the gases from the time they leave the sulfur burner 3 to the time that they enter the absorber, their temperature is conserved and maintained, the gas at no point of its travel being reduced in temperature to a point lower than the temperature required for the nextoperation. In other words, the gases are never at any point permitted to become cool so as to require any substantial artificial reheating to bring them into proper condition for the further treatments. There is, consequently, no countercurrent of the material operated on, which greatly simplifies the structure of the apparatus. The heat changes necessary in this process are all to the end of reducing temperatures and not of raising temperatures. This simplifies construction, etc. The avoidance of radical fluctuations of temperatures means that no work once accomplished requires to be undone and also that no work which is to be done requires intense auxiliary influences. The gases being maintained from the sulfur burner through to the end of the last conversion at temperatures approximating but never materially receding from the temperatures involved in the original creation of the S0 gas mixture, it will be apparent that the gas under treatment is, throughout, substantially in the same condition as when formed in the first instance, z. 6. there is no great contraction followed by great expansion and no changes of a physical or chemical nature which might be attendant upon such fluctuations of condition as would be represented by sharp contraction of temperature followed by a raising of said temperature. For example, sulfuric acid which 'might be developed, if any, would at all times be prevented from condensing and the apparatus be, in consequence, preserved against attack.

It has heretofore been considered essential that upon the creation of the S0 gas that said gas be purified not only of arsenic but of many other ingredients, such as sulfuric purifying the S gases so as to prevent them from oisoning the platinum contact material. ven when the practically pure sulfur was used as the source of 80,, it has been deemed necessary and essential to purify the gases and particularly to remove sulfur or Texas sulfur.

therefrom sulfural impurities. The removal of these impurities invariably in.- volves a reduction of the temperature of the gases so that the same, after being purified,

require a reheating to bring them up to the.

temperature required for conversion in the contact chambers.

I have now discovered that provided the temperature of the S0 gases as they leave the sulfur burner are protected against material lowering of their temperature followed by a material raising thereof, satisfactory conversion can be obtained without poisoning the contact material and without destroying the apparatus and with an efficiency equal to that of the standard process but at much less expense provided further that a certain type of sulfur is used in the burner. As illustrative of the type of sulfur which satisfies the conditions, reference is made to Louisiana brimstone and its equivalents, Freeport This material, although containing small percentages of arsenic (As O when treated in accordance with the process described and under the conditions of avoiding special purification which the described process implies,-does not result in poisoning the contact materiali-n the converters and in some of the tests which were conducted no arsenic was found in the contact material by the most refined methods, although had the full amount of the arsenic present been retained by the contact material, it would have been very easy to detect. The precise reason Why Louisiana brimstone, when treated as described, does not result in the poisoning of the contact material, cannot be definitely set down but it may be that the fact is that the percentage of arsenic in the raw material being relatively small is to a large extent retained in the ash without being volatilized, while that pro ortion which is volatilized being preserved against reduction of temperature, passes through the contact material in a condition in which it does not injure the same. Perhaps the degree of its dilution may in part account for the failure of the arsenic to act as a material factor in the poisoning of the contact material. Whatever may be the true reason-therefor, the fact is that when the source of sulfur is of the Louisiana brimstone type and the operations are conducted according to the process described, no material poisoning of the contact material takes place. The sulfuric acid mist, also recognized as a contact poison, ceases to be a factor since the temperatures of the gases are throughout kept above the condensing point of sulfuric acid. The sulfur vapor which often acts as a carrier for arsenic seems, under the special conditions of the new process, to either relinquish this function or to exercise it in a manner which is not injurious. The heat of combustion which in prior processes was sacrificed, is now conserved, only so much of it being lost as is needed to reduce the'temperatures to those required in the converters. No raising of the temperatures, which is the wasteful part of any operation, is'required. By means of this invention the use of the elaborate purifying apparatus heretofore described as necessary when using Louisiana brimstone as the sulfur dioxid source is wholly avoided. Under certain conditions, particularly faulty operation of the burner, it may be advisable to interpose a filtering device in the gas path prior to entry into the converter, to remove mechanical dust.

The practice of the procem described may, of course, within reasonable limits, be modified by occasional reduction of temperature at' various points, such temperature losses being substantially compensated for by proper heat addition, and in my claims I intend to cover such variants of the process described, it being understood that when I s eak of maintaining the temperature or of preventing the tem erature from falling below certain limits, clude that kind of temperature diminution which is characteristic of the purification processes now generally employed. So long as a substantial and material amount of the original heat of the gases e. a heat approximating or, at least, not great] -deviating from the temperature required or catalysls) is conserved and carried throughv until 97-98% falls within the intended scope of my claims.

I claim:

1. The improvement in the method of.

making sulfuric anhydrid by the contact procmean to exconversion is achieved, the process ess, which comprises employing as the raw to fall materially below the temperature required for the production of sulfuric anhydrid in the converter.

2. The improvement in the method of making sulfuric anhydrid by the contact process, which comprises employing as the raw material for the production of sulfur dioxid,'sulfur in the form of brimstone of the Louisiana brimstone type, burning the same to produce gas containing sulfur dioxid and oxygen and conducting said gas to platinum contact inaterial while maintaining a temperature in said gas above 700 F.

3. The improvement in the method of making sulfuric anhydrid by the contact process which comprises employing as the raw material for the production of sulfur dioxid, sulfur in the form of brimstone of the Louisiana brimstone type, burning the same with dried air to produce a gas containing sulfur dioxid to the extent of eight per cent. by volume and oxygen and conducting said gas to platinum contact material without permitting the temperature thereof to fall materially below the temperature required for the production of S111- furic anhydrid in the converter.

In testimony whereof I have hereunto set m hand.

y HENRY F. MERRIAM. 

